The swverify verifies the package in memory without installing the package in file system. If a package is signed, it will have the following files:
<path>/catalog/
<path>/catalog/INDEX
...
<path>/catalog/<dfiles>/md5sum
<path>/catalog/<dfiles>/sha1sum
<path>/catalog/<dfiles>/sig_header
<path>/catalog/<dfiles>/signature
...
For example:
swverify -d @- <somepackage-1.0.tar.gz
# - or -
swverify <somepackage-1.0.tar.gz